Upgrade vscode-extension-tester and use latest Node 18 for tests

Closes #683

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

.github/workflows/tests.yml

@@ -23,7 +23,7 @@ jobs:
         uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: '18.15'
+          node-version: '18'
       - name: Install vsce
         run: npm i -g @vscode/vsce
       - name: Install dependencies